It is known to enlarge the lumen or flow cross section of an artery by the use of a thrombectomy catheter which has a drilling or milling tool rotatable, e.g. by an electric motor, and a tube at the end of which the tool is provided.
A guide probe can be inserted into the artery and can include one or more wires to serve as a guide for this tube. For this purpose the tool can have a passage extending axially therethrough to enable relative axial movement of the tool and tube on the guide probe.
For exact guidance and positioning of the thrombectomy catheter in the artery to be subjected to thrombectomy, the guide probe is initially inserted into the artery and the movement of the guide probe therealong is monitored by radiography, e.g. X-ray.
In a conventional embodiment of the thrombectomy catheter, as soon as the guide probe reaches an arterial constriction or blockage, a tube is passed over the guide probe to that constriction or obstruction, the tube having at its leading end a tool having an axial bore.
The guide probe is then retracted from the artery through the tube and a flexible drive shaft is inserted into the tube. The drive shaft comprises a coupling member at its leading end which engages in a corresponding countermeasure of the tool in an indexing manner.
When the drive shaft is coupled with the tool, the tool is set into rotation via the drive shaft and is advanced together with the tube to enlarge the lumen of the artery by a cutting operation.
This thrombectomy catheter is indeed effective although its use is time-consuming because it requires threading the tube onto the guide probe, withdrawal of the guide probe, threading a -drive shaft through the tube and like operations which are time-consuming. Furthermore, some of these operations may be threatening to the well-being of the patient.
U.S. Pat. No. 4,700,705 describes a thrombectomy catheter having a tool at the leading end of a tube. The tool here is formed with a cylindrical axial bore through which a guide probe can be fed. The drive of the tool head, however, is effected by a separate drive shaft coaxial with the guide probe.
This construction is relatively complex. Furthermore, because of the complex mechanism, there is no free space for a circulation of the blood and for the transportation of excised material from the constriction or obstruction.
Similar problems are encountered with the catheter of European patent publication EP-0 191 630 in which the drive of the tool is effected by a turbine directly adjacent the tool itself.